Made available in DSpace on 2014-12-17T14:06:54Z (GMT). No. of bitstreams: 1 SheilaBG_DISSERT.pdf: 1652158 bytes, checksum: ad653b0a72284122fdd7e2e051380eb2 (MD5) Previous issue date: 2010-04-23 / Universidade Federal do Rio Grande do Norte / In this study barium hexaferrite was (general formulae BaFe12O19) was synthesized by the Pechini method under different conditions of heat treatment. Precursors like barium carbonate and iron nitrate were used. These magnetic ceramic, with magnetoplumbite type structure, are widely used as permanent magnet because of its excellent magnetic properties, such as: high Curie temperature, good magnetic anisotropy, high coercivity and corrosion resistance. The samples were characterized by thermal analysis (DTA and TG), X- ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) end Vibrating sample Magnetometer (VSM). The results confirm the expected phase, which was reinforced according to our analysis. A single phase powder at relatively high temperatures with particle sizes around 100 nm was obtained. The characteristic magnetic behavior one of the phases has been noted (probably superparamagnetic material), while another phase was identified as a ferrimagnetic material. The ferrimagnetic phase showed vortex configuration with two central and slightly inclined plateaus. In general, increase of heat treatment temperature and time, directly influenced the technological properties of the samples / Neste trabalho foi sintetizado o composto da Hexaferrita de B?rio de f?rmula geral BaFe12O19, preparado pelo m?todo Pechini (sob diferentes condi??es de tratamento t?rmico), utilizando-se como precursores o carbonato de b?rio e o nitrato de ferro. Estes materiais cer?micos magn?ticos, com estrutura do tipo magnetoplumbita, s?o amplamente utilizados como magnetos permanentes, devido as suas excelentes propriedades magn?ticas, tais como: alta temperatura de Curie, boa anisotropia magn?tica, alta coercividade e resist?ncia ? corros?o. As amostras obtidas foram caracterizadas pelas t?cnicas: An?lises T?rmicas (DTA e TG), Difra??o de raios-X (DRX), Espectroscopia de absor??o na regi?o do infravermelho (FTIR), Microscopia Eletr?nica de Varredura (MEV) e Magnet?metro Vibracional (VSM). Os resultados mostraram a fase desejada, onde foi intensificada de acordo com as an?lises realizadas, resultando na obten??o de um p? monof?sico nas temperaturas relativamente altas com tamanhos de part?culas em torno de 100 nm. Os materiais possuem fases de comportamento magn?tico caracter?stico, provavelmente de um material superparamagn?tico e outro ferrimagn?tico que em temperaturas mais elevadas apresentaram uma configura??o de v?rtice, com dois plat?s centrais com pequenas inclina??es. De modo geral, os aumentos da temperatura de tratamento t?rmico e do tempo, influenciaram diretamente nas propriedades tecnol?gicas das amostras